Volume stores are used in internal combustion engines, in order for it to be possible to satisfy brief consumption peaks of hydraulic medium. One field of use lies, for example, in the area of camshaft adjustment, by way of which a phase position between a crankshaft and a camshaft can be configured in a variable manner.
The camshaft adjuster is integrated into a drive train, via which torque is transmitted from the crankshaft to the camshaft. The phase adjustment usually takes place by means of a hydraulic actuating drive which is fed with pressure medium by a pressure medium pump of the internal combustion engine. If rapid phase adjustments over a large phase angle are required during the operation of the internal combustion engine, the required pressure medium volume can exceed the pressure medium volume which is conveyed by the pressure medium pump. In this case, the difference is provided from the volume store. Furthermore, the volume store assists the camshaft adjustment in operating phases, in which the speed-dependent delivery volume of the pressure medium pump is too low to sufficiently supply the camshaft adjuster. This is usually the case at low speeds and high pressure medium temperatures. Moreover, the volume store assists the camshaft adjuster when a basic position is reached during the switch off operation of the internal combustion engine.
A volume store for assisting a camshaft adjuster is known, for example, from DE 102 28 354 A1. The volume store is arranged in a cavity of a camshaft, a piston being arranged within the cavity such that it can be displaced axially against a pneumatic spring. The pressure medium feed to the camshaft adjuster and the volume store takes place via a common feed line via a camshaft bearing. During the operation of the internal combustion engine, the volume store is filled in operating phases of low pressure medium consumption. This pressure medium volume which is stored in the volume store is available to the camshaft adjuster in operating phases with relatively high pressure medium consumption. In order to prevent pressure medium from flowing out of the volume store in the direction of the pressure medium pump, a nonreturn valve is usually provided upstream of the camshaft bearing. This is disclosed, for example, in DE 10 2007 056 683 A1, in which the method of operation of a camshaft adjuster of vane cell design is also explained.